Manual Webspam Error. Same Penalty On All Sites On Webmaster Tools Acc

Today when i checked webmaster tools under manual spam section. I got Manual spam and reason was Thin content with little or no added value. Then I checked other sites from same webmaster tools account, there are 11 sites, all of them received same manual action. I never received any mail, no notification on site messages section regarding this manual action.

I just need confirmation whether it is something to do with any error in webmaster tools or all of the sites really received manual spam actions.

Most of the article on sites are above 500 words, quality content (no spun or copied).

What makes you think that having more than "500 words" is going to make an "article" not be considered "thin" content?

Any fool can waffle on to reach a pre-determined "word count" and say absolutely nothing useful at all, which is what 'thin' content really is. But a good writer or orator can create wonderful quality content in a couple of paragraphs.

Given the clues that you unwittingly provide, I would surmise that the content on all your sites has been written to an "S.E.O. formula" of 'X' number of words with a 'key' word 'density' of "Y" percent, by a writer who's grasp of the English language is somewhat less than 'good', which is a perfect recipe for failure.